Semiconductor substrates, particularly, semiconductor wafers, will be contaminated if dusts, vaporized organic substances, or others (hereafter simply referred to as “dusts”) adhere to those substrates. This contamination will have influence on the manufacture, such that in particular, a yield ratio, or a rate of non-defectives in manufacturing those substrates is reduced. Accordingly, carrying semiconductor wafers requires that the surroundings thereof be high in a clean level. This means that semiconductor wafers can be categorized into one of the objects (hereinafter referred to as a dust-free object) of which clean levels should be kept high during the carriage.
In general, semiconductor wafers are processed in what is called a clean room, which is a room cleaned at a higher level (hereafter referred to as a “high clean room”). In contrast, in cases where semiconductor wafers should be delivered in a room or others whose clean levels are lower, the wafers are contained in a highly cleaned airtight container (hereafter referred to as a “container”), and the container itself is carried. This delivery enables semiconductor wafers to be carried by way of a room or an outside environment that is lower in the clean level room (hereafter referred to as a “lower-clean-level room”), with the wafers unpolluted by dusts during their carriage.
A loader having an aperture that can be closed is arranged at a boundary between a high clean room and a lower-clean-level room. The loader is used not only for carrying in semiconductor wafers from the highly cleaned space in a container to a highly cleaned room for processing the wafers (hereafter referred to as “loading”). The loader is also used for carrying out the semiconductor wafers from the highly cleaned room to the highly cleaned space in the container in order to deliver the processed wafers to another step (hereafter referred to as “unloading”).
For loading or unloading semiconductor wafers, the wafers are carried in or out through the aperture of the loader. The container is equipped with a lid so as to be located at the aperture of the loader, so that the lid is taken off when semiconductor wafers are carried in or out.
As standards for such containers and loaders, proposed and employed are SEMI (Semiconductor Equipment and Material International) standard E47.1 “Box/Pod (FOUP),” E15.1 “Tool Load Port,” E57 “Kinematic Coupling,” E62 “Front-Opening Interface Standard (FIMS),” E63 “Box/Opener to Tool Standard (BOLTS),” (hereinafter referred as “the standards”).